This invention relates to a method for prepressurizing a dispensing container and for filling a pressurized container with flowable product.
It is well known to dispense flowable products from a container such as an aerosal can by internal pressure that forces the product out through a nozzle when a valve is manually actuated. In a particularly desirable pressure generating system, a confined chemical reaction causes gas to be produced within the dispensing container without the reagents coming into contact with the product to be dispensed and without the release of the reagents or the gas to the atmosphere. In one such pressure generating system, as disclosed in U.S. Pat. Nos. 4,360,131 to Reyner, 4,376,500 to Banks et al. and 4,478,044 to Magid, different chemical reactants such as citric acid and sodium bicarbonate react with one another to form a gas such as carbond dioxide to expand an inflatable pouch.
U.S. Pat. No. 4,478,044 discloses an inflatable pouch for use in a dispensing container to provide pressure as the result of a repeated series of chemical reactions that release gas within the pouch each time a certain volume of product is dispensed through an outlet valve on the container. In a particular embodiment of the inflatable pouch, a pair of outer walls are permanently sealed around their peripheries to one another. The pouch contains a burstable bag holding a predetermined quantity of a first chemical reagent in liquid form. The pouch also contains a partly hydrolyzed polyvinyl alcohol ("PVA") bag holding a second chemical reagent preferably in the form of a powder. Immediately prior to the insertion of the pouch into a container through an open end thereof, the burstable bag is ruptured. Upon the release of the liquid reagent into contact with the PVA packet, the material of that packet dissolves and allows the powdered chemical reagent to come into contact with the liquid reagent, whereby a gas is generated to expand the pouch. This initial expansion commences only upon a delay equal to the time required for the water or other solvent to dissolve the PVA packet. During the delay, the container is filled with a flowable product and is sealed by a cap or lid containing a valve. Upon dispensing of a portion of the product through the valve, the pouch expands under the pressure generated by the initial gas generation. This pouch expansion causes the separation of a releasable seal between a base sheet and a cover sheet disposed inside the pouch together with the burstable bag and the PVA packet, the separating of the seal serving to release further quantities of one of the reagents from a series of pockets provided in the base sheet. The pockets are opened in seriatum as greater and greater amounts of product are dispensed from the container.
Pouches such as those disclosed in U.S. Pat. No. 4,478,044 are useful insofar as they may be shipped independently of the dispensing containers. However, the method of filling a can with a flowable consumer product, inserting an expandable pouch into the can and then crimping a cap with a valve on the can to seal it has several disadvantages. In particular, during the sealing of the can, air becomes trapped in the can and can interfere with the product and the dispensing process. Moreover, pouch shelf life is limited by the longevity and integrity of the seals insofar as the pouches cannot be used until the time the cans are to be filled with product. A further disadvantage is that the pouches must be inserted into the cans at the same production site at which the cans are filled with product, which requires that each product packaging facility must be equipped with on-site pouch insertion machinery.